Density-functional calculation of the shock Hugoniot for diamond

Abstract

The principal Hugoniot of diamond is calculated using density-functional molecular dynamics. Using existing ab initio melt lines, diamond is predicted to melt on its Hugoniot in the range of $700--745\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The shock compression of diamond into a high-density conducting liquid phase has an associated 13%--14% density increase across its coexistence region. Complete band gap closure before the onset of melting is not observed within these calculations. The importance of two simulation parameters necessary for obtaining quantitatively accurate predictions in the liquid carbon phase is identified: electronic temperature and supercell size. Our results expound upon existing laser-driven shock experiments and provide valuable equation of state data relevant to future high-pressure physics experiments.